One patient was enrolled in protocol 438, an evaluation of maxillary sinus treatments in patients with antrostomies, before 11/30/95. This was a 35 year-old woman with cystic fibrosis. Her genotype was compound heterozygote. Results are preliminary. Nasal mucosa transepithelial potential differences are similar to maxillary sinus transepithelial potential differences except that maxillary sinus transepithelial potential differences, during baseline determinations, are more sensitive to the effect of local chronic infection.